Mediterranean diet beats traditional dietary advice in IBS
Researchers say the diet could serve as a first-line dietary option for people with IBS.
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12/02/2025
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by Doug Brunk
Among individuals with irritable bowel syndrome (IBS), the Mediterranean diet proved superior to established traditional dietary advice and achieved response rates comparable to those typically expected from the low fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAP) diet, according to a randomized trial.
“IBS patients rank dietary options as a top research priority, yet evidence-based choices are limited,” senior author Imran Aziz, MBChB, MD, a Consultant Gastroenterologist at the University of Sheffield, United Kingdom, told GI & Hepatology News. “Most patients receive traditional dietary advice as first-line therapy (with only 40% responding), with non-responders escalated to the complex, restrictive low FODMAP diet requiring specialist dietetic supervision. This study addresses whether the Mediterranean diet, which is easier to implement and has established broader health benefits, could serve as an effective first-line alternative.”
The study, published in the Annals of Internal Medicine, enrolled 139 adults across the United Kingdom who met Rome IV criteria for IBS and scored 75 or greater on the IBS Symptom Severity Scale (IBS-SSS). The researchers randomized participants 1:1 to 6 weeks of traditional dietary advice or the Mediterranean diet delivered via an online group education model, a pragmatic design reflecting real-world clinical practice. The primary endpoint was a 50-point or greater reduction on the IBS-SSS.
The researchers reported that 62% of participants assigned to the Mediterranean diet achieved the primary endpoint, compared with 42% receiving traditional dietary advice. The between-group difference favored the Mediterranean diet by 20%, demonstrating not only noninferiority but statistical superiority.
For the secondary endpoint of a 100-point or greater reduction on the IBS-SSS, response rates again numerically favored the Mediterranean die (44% vs. 32%), but this difference did not reach statistical significance. Mean improvement in IBS-SSS was significantly greater with the MD than with TDA (−101.2 vs. −64.5), with the largest separation appearing at the 6-week mark. Symptom improvements emerged early, with both groups showing significant reductions by week 2.
In other findings, both groups improved across IBS-SSS components of pain, bloating, bowel dissatisfaction, and interference with life. Only frequency of abdominal pain showed a statistically greater benefit with the Mediterranean diet. Measures of mood based on the Patient Health Questionnaire-4, somatic symptom burden based on the Patient Health Questionnaire-12, and quality of life based on the Short Form-8 Health Survey improved within groups but did not differ significantly between diets. Diet satisfaction was comparable between both groups.
The authors noted that the mechanism by which the Mediterranean diet alleviates IBS symptoms remains unclear. “Whether there is a specific or synergistic effect of the [Mediterranean diet] in beneficially regulating the microbiome–gut–brain axis warrants investigation,” they wrote. “For example, the [Mediterranean diet] positively affects the gut microbiome, and some of its ingredients, such as olive oil, possess anti-inflammatory and antioxidant properties, while also reducing visceral hypersensitivity in animal models.”
Aziz acknowledged certain limitations of the trial, including the inability to blind participants to their assigned diets, the 6-week duration which limits assessment of long-term benefits, and exclusion of those under 18 or over 65 years old. “The Mediterranean diet is widely available, culturally acceptable, and has numerous established health benefits,” he said. “This makes it an attractive first-line option for IBS that patients can implement without requiring specialist dietetic support.”
The researchers had no relevant disclosures.
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The guidelines emphasize four-hour gastric emptying studies over two-hour testing. How do you see this affecting diagnostic workflows in practice?
Dr. Staller: Moving to a four-hour solid-meal scintigraphy will actually simplify decision-making. The two-hour reads miss a meaningful proportion of delayed emptying; standardizing on four hours reduces false negatives and the “maybe gastroparesis” purgatory that leads to repeat testing. Practically, it means closer coordination with nuclear medicine (longer slots, consistent standardized meal), updating order sets to default to a four-hour protocol, and educating front-line teams so patients arrive appropriately prepped. The payoff is fewer equivocal studies and more confident treatment plans.
Metoclopramide and erythromycin are the only agents conditionally recommended for initial therapy. How does this align with what is being currently prescribed?
Dr. Staller: This largely mirrors real-world practice. Metoclopramide remains the only FDA-approved prokinetic for gastroparesis, and short “pulsed” erythromycin courses are familiar to many of us—recognizing tachyphylaxis limits durability. Our recommendation is “conditional” because the underlying evidence is modest and patient responses are heterogeneous, but it formalizes what many clinicians already do: start with metoclopramide (lowest effective dose, limited duration, counsel on neurologic adverse effects) and reserve erythromycin for targeted use (exacerbations, bridging).
Several agents, including domperidone and prucalopride, received recommendations against first-line use. How will that influence discussions with patients who ask about these therapies?
Dr. Staller: Two points I share with patients: evidence and access/safety. For domperidone, the data quality is mixed, and US access is through an FDA IND mechanism; you’re committing patients to EKG monitoring and a non-trivial administrative lift. For prucalopride, the gastroparesis-specific evidence isn’t strong enough yet to justify first-line use. So, our stance is not “never,” it’s just “not first.” If someone fails or cannot tolerate initial therapy, we can revisit these options through shared decision-making, setting expectations about benefit, monitoring, and off-label use. The guideline language helps clinicians have a transparent, evidence-based conversation at the first visit.
The guidelines suggest reserving procedures like G-POEM and gastric electrical stimulation for refractory cases. In your practice, how do you decide when a patient is “refractory” to medical therapy?
Dr. Staller: I define “refractory” with three anchors.
1. Adequate trials of foundational care: dietary optimization and glycemic control; an antiemetic; and at least one prokinetic at appropriate dose/duration (with intolerance documented if stopped early).
2. Persistent, function-limiting symptoms: ongoing nausea/vomiting, weight loss, dehydration, ER visits/hospitalizations, or malnutrition despite the above—ideally tracked with a validated instrument (e.g., GCSI) plus nutritional metrics.
3. Objective correlation: delayed emptying on a standardized 4-hour solid-meal study that aligns with the clinical picture (and medications that slow emptying addressed).
At that point, referral to a center with procedural expertise for G-POEM or consideration of gastric electrical stimulation becomes appropriate, with multidisciplinary evaluation (GI, nutrition, psychology, and, when needed, surgery).
What role do you see dietary modification and glycemic control playing alongside pharmacologic therapy in light of these recommendations?
Dr. Staller: They’re the bedrock. A small-particle, lower-fat, calorie-dense diet—often leaning on nutrient-rich liquids—can meaningfully reduce symptom burden. Partnering with dietitians early pays dividends. For diabetes, tighter glycemic control can improve gastric emptying and symptoms; I explicitly review medications that can slow emptying (e.g., opioids; consider timing/necessity of GLP-1 receptor agonists) and encourage continuous glucose monitor-informed adjustments. Pharmacotherapy sits on top of those pillars; without them, medications will likely underperform.
The guideline notes “considerable unmet need” in gastroparesis treatment. Where do you think future therapies or research are most urgently needed?
Dr. Staller: I see three major areas.
1. Truly durable prokinetics: agents that improve emptying and symptoms over months, with better safety than legacy options (e.g., next-gen motilin/ghrelin agonists, better-studied 5-HT4 strategies).
2. Endotyping and biomarkers: we need to stop treating all gastroparesis as one disease. Clinical, physiologic, and microbiome/omic signatures that predict who benefits from which therapy (drug vs G-POEM vs GES) would transform care.
3. Patient-centered trials: larger, longer RCTs that prioritize validated symptom and quality-of-life outcomes, include nutritional endpoints, and reflect real-world medication confounders.
Our guideline intentionally highlights these gaps to hopefully catalyze better trials and smarter referral pathways.
Dr. Staller is with the Division of Gastroenterology, Massachusetts General Hospital and Harvard Medical School, Boston.